There is an increasing demand for water suitable for drinking and irrigation. Consequently there is an increasing demand for purifying impure water, such as sea water.
German Patent Application No. 10230668 describes a scheme for purifying “raw” water in which air is humidified as it passes across an arrangement of rods while the raw water is dripped over the surface of the rods. A condenser is then used to extract purified water from the humidified air.
European Patent Application No. 1 362 833 A2 discloses a water purification apparatus comprising a water source and a hydrophilic membrane. The hydrophilic membrane allows water to pass through the membrane as a vapour, and prevents impurities passing through. That patent specification contains a description of suitable hydrophilic materials, and also the results of experiments conducted in using bags made from hydrophilic material for irrigating plants.